Our invention relates to orthopedic surgical guides and jigs. Specifically our invention is a clamp and saw guide for holding a human patella and providing a guide so that a predetermined portion of the patella may be accurately removed by sawing.
The two largest and longest bones of the human body, the femur and tibia, meet at a person's knee. The tibia is situated at the front and inner side of the lower leg. It is prismoid in form, and expanded above where it enters into the knee joint. The head of the tibia is large and expanded on each side into two eminences, the condyles. These eminences form two smooth concave compartments or surfaces which articulate with the condyles of the femur. The medial condyle is more prominent anteriorly and broader both in the anterior-posterior and transverse diameters than the lateral condyle. Accordingly, the lateral articular surface of the tibia is shorter, more shallow and narrower than the medial surface of the tibia. The medial surface is broader, more circular, and concave from side to side. The anterior surfaces of the tuberosities are continuous with one another, forming a single large surface which is somewhat flattened. Posteriorly the tuberosities are separated from each other by a shallow depression for attachment of ligaments. The medial tuberosity presents posteriorly a deep transverse groove for the insertion of a tendon.
The patella is a sesamoid or lens shaped bone which slides in a groove between the condyles of the femur. Its function is to increase the efficiency of the quadriceps muscle by shifting the line of action of the muscle's pull forward. As the knee articulates, the muscles and tendons force the patella toward the condyles of the femur. Consequently, there is considerable relative motion between the patella and the other bones comprising the knee joint.
Because of aging or disease, the articulating surfaces of the knee may degrade. To treat certain pathologies, it has become common to surgically remove the condyles and replace these structures with prosthetic implants. By the same processes, the articulating surfaces of the patella may also degrade. In connection with the implantation of a prosthetic knee, therefore, the articulating surface of the patella may also be replaced. Because of the tendons connected to the patella, it is generally advisable to replace only the articulating surface. An ultra high molecular weight polyethylene articulating surface, with or without a metal baseplate, will be implanted on the posterior side of the patella, adjacent the femoral condyles. To implant such a prosthesis, the posterior surface of the patella is resected to produce a flat surface upon which the prosthesis can be mounted. In the past, the surgeon has often relied on skill of hand and eye in manipulating a sagittal saw to make an appropriate cut.